docs: def pdflookup(pdf, allresults, outformat, startpage=None):
      """Look a pdf up on google scholar and return bibtex items.
  
      Paramters
      ---------
      pdf : str
          path to the pdf file
      allresults : bool
          return all results or only the first (i.e. best one)
      outformat : int
          the output format of the citations
      startpage : int
          first page to start reading from
  
      Returns
      -------
      List[str]
          the list with citations
  
      """
      txt = convert_pdf_to_txt(pdf, startpage)
      # remove all non alphanumeric characters
      txt = re.sub("\W", " ", txt)
      words = txt.strip().split()[:20]
      gsquery = " ".join(words)
      bibtexlist = query(gsquery, outformat, allresults)
      return bibtexlist